The present invention relates to a control system for a humidity controller for tobacco leaves, particularly to a control system for a humidity controller in which the water content and temperature of the tobacco leaves are controlled to a given value in the material treatment.
In general tobacco production process, tobacco leaves used for raw material are separated each other and are provided with a flexibility by the addition of water and steam. Thereafter they are separated into the ligneous parts (or ribs) and the parenchyma (or laminae). The laminae are dried to possess 12% of water content for avoiding change in quality and molding during long term storage and then packed in a barrel or other container (above-mentioned process be referred to as a raw material treating process). The packed laminae are stored for a long time for maturing. The laminae which have finished maturing are threshed into cut cigarett after the steps of leaf orientation, blending and flavoring.
During the raw material treating process, a flexibility necessary to rib removing is imparted to the tobacco leaves by providing water and steam thereto when they are passed through a cylindrical humidity controller. The amount of water and steam gives a great influence upon yield and quality of raw material. In other words the tobacco leaves are subjected to great mechanical action, when they are separated into laminae and ribs. Accordingly separation between laminae and ribs is not sufficiently accomplished, or conversely excessive separation is accomplished so that the tobacco leaves are finely divided depending upon the physical properties possessed by the tobacco leaves. Therefore it is most important to control the water content and temperature of the tobacco leaves within a predetermined range, which have a strong relation with the physical properties of the tobacco leaves.
Operation of the humidity controller has heretofore been manually controlled. The water content and temperature of the tobacco leaves at the exit of the humidity controller are measured by the sense of touch of an operator to compare them to the preset values. The operator operates values to change the amount of water and steam to be added where there is a deviation therebetween. However measurement of the water content and temperature of the tobacco leaves by the sense of touch requires long experience and good perception of the operator. It is almost impossible to manually control the water content and temperature at the exit of the humidity controller at constant levels since the water content of the tobacco leaves varies from 9% to 21% by wetting standards at a cycle of 30 seconds to one minute and the humidity controller has a time lag of approximately three minutes and dead time of approximately two minutes.